Understanding the genetic basis of biodiversity: Sexual selection, gene expression and primate pigmentation.

人类和黑猩猩有近99%的基因组相同，但在外观和认知方面却表现出惊人的差异。在一些蝴蝶物种中，在不同环境中发育的遗传相同的个体可以有显着不同的翅膀颜色。这些例子说明，很少的遗传多样性可以产生很高的生物多样性。为了了解这是如何发生的，生物学家正在将重点从研究基因序列转移到研究基因如何以及何时表达。利用生物医学科学的最新技术进步，基因表达研究现在提供了前所未有的机会，以了解密切相关和遗传相似的动物物种在外观和行为上如何如此不同。我的研究检查灵长类动物毛囊中的基因表达，以了解毛发色素沉着变异的遗传基础。了解动物色素对于了解动物生物学的许多方面至关重要，包括物种形成事件（密切相关的物种之间的色素差异是物种分裂的原因还是结果？），自然选择和性选择之间的权衡（显眼的颜色可以吸引配偶和警告竞争对手，但也会增加被捕食的风险），以及合作行为的进化（独特的颜色可以让个体相互识别并确定其亲属）。灵长类动物的色素沉着是特别有趣的，因为灵长类动物可以说是最丰富多彩的哺乳动物，经常显示出明显的颜色差异之间的密切相关的物种，种群内的个体之间，男性和女性之间，以及婴儿和成人之间。尽管达尔文在世纪前就认识到了灵长类动物颜色多样性在进化上的重要性，但令人惊讶的是，从那以后，这个话题就很少受到研究的关注。我正在研究一系列灵长类动物（人类，猿，新旧世界的猴子和原猴）的毛发，以确定不同颜色的毛发在其基因表达模式中的色素沉着途径。我正在采取一种候选基因的方法，专注于大约20个色素相关基因，选择这些基因是因为它们已知参与决定小鼠的毛色，还有两个参考基因作为对照。通过测量和比较来自许多个体的各种颜色毛囊中每个基因特异性的基因产物（RNA）的相对量，我可以确定基因表达和头发颜色之间的关联。研究结果应该能让我们深入了解进化是如何修补有限的遗传变异，从而产生如此多样的形式。最终，我计划比较灵长类动物毛发着色的遗传基础，以评估这种“修补”在不同分类群中的一致性或可变性。例如，我计划比较红头发和黑发的人，黑猩猩和猩猩，黑吼猴和红吼猴，黑皱狐猴和红皱狐猴的红毛和黑发。确定哪些色素沉着基因是灵活的（在不同的类群），哪些是保守的（在不同的类群），在他们的表达模式是一个明显的第一步，了解色素沉着如何影响和自然选择和性选择的影响。

Humans and chimpanzees share nearly 99% of their genomes, yet show striking differences in appearance and cognition. In some butterfly species, genetically identical individuals developing in different environments can have remarkably different wing coloration. Such examples illustrate how high levels of biological diversity can arise from very little genetic diversity. To understand how this occurs, biologists are shifting the focus from studying gene sequences to studying how and when genes are expressed. Taking advantage of recent technical advances developed in biomedical science, gene expression research now provides unprecedented opportunities to understand how closely related and genetically similar animal species can be so different in appearance and behaviour. My research examines gene expression in the hair follicles of primates to understand the genetic basis of variation in hair pigmentation. Understanding animal pigmentation is crucial to understanding many aspects of animal biology, including speciation events (are pigmentation differences between closely-related species a cause or a consequence of the species split?), the trade-offs between natural and sexual selection (conspicuous colours can attract mates and warn rivals but also increase the risk of predation), and the evolution of cooperative behaviours (unique coloration may allow individuals to recognize each other and identify their relatives). Primate pigmentation is especially interesting as primates are arguably the most colourful mammalian order, often showing marked colour differences between closely-related species, between individuals within populations, between males and females, and between infants and adults. Although Darwin recognized the evolutionary importance of primate colour diversity over a century ago, the topic has received surprisingly little research attention since. I am examining hairs from a range of primates (humans, apes, New and Old World monkeys, and prosimians) to identify where in the pigmentation pathway hairs of different colours diverge in their patterns of gene expression. I am taking a candidate gene approach focusing on about 20 pigment-related genes, selected because of their known involvement in determining coat colour in mice, and two reference genes to serve as controls. By measuring and comparing the relative amounts of gene product (RNA) specific for each gene in hair follicles of various colours from numerous individuals, I can identify associations between gene expression and hair colour. Results should provide insights into how evolution tinkers with a limited amount of genetic variation to produce such a great diversity of forms. Ultimately, I plan to compare the genetic basis of hair coloration across primates to assess how consistent or variable this 'tinkering' is across taxa. For example, I plan to compare red and black hair in red-headed vs. brunette humans, in chimpanzees vs. orangutans, in black howler monkeys vs. red howler monkeys, and in black ruffed lemurs vs. red ruffed lemurs. Identifying which pigmentation genes are flexible (vary across taxa) and which are conserved (similar across taxa) in their expression patterns is an obvious first step to understanding how pigmentation influences and is influenced by natural and sexual selection.